This research is concerned with understanding the physiology of the mammalian sense of taste including the processing and stability of the sensory information transmitted to the brain. The dominant focus of concern is to elucidate the nature of the plasticity in the taste system evident both in taste receptor regeneration and turnover in the normal adult mammal. The interactions between taste nerve fibers and epithelial cells, which are precursors of taste receptor cells, lead to the differentiation and maintenance of the receptor cells (trophic dependence upon the nerve supply) and the formation of appropriate synaptic connections with the receptor cells. This research will evaluate a) the role of axonal transport in the maintenance of taste receptor cells, b) the consequences of hyperinnervation of taste receptor cells, c) the functional capabilities of the central branch of taste axons to reinnervate taste receptor cells, and d) the cholinergic modulation of taste sensory input. Understanding the mechanisms of neurotrophic maintenance and regeneration of taste receptor cells may improve our ability to prevent degeneration and to aid recovery in impaired neural and sensory systems.